


The Grey Matter

by anchors



Category: Sherlock (TV)
Genre: -Ish, AU, M/M, SCIENCE!, casefic
Language: English
Status: Completed
Published: 2012-08-28
Updated: 2012-08-28
Packaged: 2017-11-13 01:28:51
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 19,821
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/497916
Author URL: https://archiveofourown.org/users/anchors/pseuds/anchors
Summary: <blockquote class="userstuff">
              <p>Written for the FuckYeahJohnlockFanfic blog's August CaseFic/Experiment Contest. Sherlock is hired by his brother to find a cure for the strange phenomenon John Watson has unwittingly brought into their world, but it's immediately clear there's more to this case - and more to this man - than meets the eye. AU, ish.</p>
            </blockquote>





	The Grey Matter

**Author's Note:**

  * Translation into Русский available: [В сером cвете](https://archiveofourown.org/works/537861) by [dzenka](https://archiveofourown.org/users/dzenka/pseuds/dzenka)



> Written for the FuckYeahJohnlockFanfic blog's August CaseFic/Experiment Contest. Had this idea ages ago and intended to do my usual overtly-flowery, maybe 4000 word synthesis, but then the contest came along and my whole brain decided to punch me in the face and go for it. Thus it should be noted that casefics are way harder than anticipated, but let's be honest - I spent half my time chortling over _50 Shades of Grey_ and _A Study in Scarlet_ puns, with a side of _Pleasantville_ for good measure, so it was a fun little experience nonetheless.
> 
> 090812 Edit - We won! Ahh! Devin's lovely cover is featured below. Thank you all so much for your support of this fic <3
> 
> 031813 Edit - Lovely cover by otterymary added below - sorry it took me so long to get it up here, dear!

 

 

 

(c) otterymary

***

 

(c) devinleighbee

***

 

 

In this world there is black and there is white, and not only in the sense of false dilemma. In this world there are a hundred, a thousand, a million other alternatives banding between the two, an infinite space between the dark and the light. And in this world, that is all there is.

In the sky, clouds are white; in the summer before the sun sets it's the clarity of glaciers sliding across a background indiscernible from the masses buffeted by wind. During storms, though, they darken, gunmetal bleeding out from the darker shadows, until the whole sky is roiling slate and onyx and obsidian by the edges of the night-time world.

Lamp-posts are black. Charcoal is, predictably, charcoal. Doves are white.

But so are trees. And grass. And fire.

The woman down the street might ask for #413839 when she paints the living room, and the man at the house on the corner might go for #736F6E. The people walk the cobblestone streets of Ash and Battleship, look at shopfronts of Cadet and Mountain Air. Those same people have eyes but they are mercury or cinder or ebony.

There is no green. There is no blue. And here there is nothing wrong with that.

In this world there are trillions of variations that emerge from black and white ends of a solid spectrum, and nothing more; nothing until John Watson.

 

 

The guard swipes his key card and the door buzzes loudly in the silence. The access pass goes back in his pocket, and in the manner of all obedient soldiers he turns a blankly pleasant face to his companion.

"This is as far as my clearance goes, sir," he says. He pushes the door aside, propping it open and gesturing down a wide corridor with low ceilings. "He'll meet you at the end."

Sherlock steps through the opening, pausing to allow his eyes to adjust to the darkness. Dim lights vanish into the distance as the tunnel slopes away. He turns back, quizzical eyebrow raised. "And where will I find the end?"

The other man's eyes dart nervously to his side before fixing on a space just above Sherlock's head. "Just keep walking."

The eyebrow lurches higher, but it's abundantly clear this man - early twenties, nervous tremor, all the marks of young service and naivete - is going to be of little use. He rolls his shoulders back and steps through the opening, but he's hardly gone three paces when the young soldier calls out to him.

"Sir! I think you should know... it's not where you'll find the end, but - what you'll find." He sounds uncertain, twisting his beret in his hands before he seems to snap to attention and draw away, the door closing with a reverberating clank behind him.

Odd. And somehow, all the more potential in that. He starts forward again, new eagerness in his step as he makes his way down the yawning throat of the musty underground passage.

His feet echo on the cement, little splashes against his soles telling him of the pipes that must lead here from above ground. But even squinting above and before him it's just a mass of the same shadeless inky black, his way only marked by the shuddering, uneven light of the bleak fluorescents. No doors, no air from tunnels breaching from his own dark passage. It's true then, that there's something here the government is very, very desperate to keep hidden.

Something different is here. Something new.

The figure at the end of the corridor, however, is not. Propped smoothly against a door similar to the one he'd just entered is a man in an expensive suit, the eerie light flickering over his head doing nothing to mar the air of undaunted calm that seems to seep from all sides, right down to the absent, bored tapping of an umbrella's brass tip.

"Expecting rain?" he asks, drawing the man's attention up from his watch. He smirks without any feeling behind the gesture, pocketing the device and standing straight.

"Storms of a different kind, dear brother," he says, voice even, and Sherlock narrows his eyes. "Shall we?" He doesn't wait for an answer, and Sherlock sees the flash of another card before this door unlocks and Mycroft gestures him inside.

It's lighter here, he immediately realizes, but not by much - and that's only due to the laboratory conditions of the room they've entered, with its crisp, unheated light and whitewashed walls. It's actually more of another hallway itself, with glass rooms on all sides facing inwards, separated by what seems to be reinforced steel and concrete. The glass, upon closer inspection, proves bullet-proof.

"Top-secret, as I'm sure you're aware," his brother adds from his side, and Sherlock snorts.

"Yes, the access cards and dramatic cavern were hardly an indicator of that." He sweeps away, already peering into the tiny rooms at his sides. Cages, more like. Also interesting. But not two steps in and he pulls up short. Turning back to Mycroft, inquires, "Why is it top-secret if they're all empty?" The look in his eyes sharpens. "No dust. Still running the electricity. This is recent then, so you've had to move everything. But what stayed? Why -" He turns, coat sweeping around his knees as if splaying out towards the far edges of the room just as much as his darting eyes, probing into the dark.

And there, at the end. A light.

He stops, sharp, and perhaps even forgets to breathe. Doesn't matter. That's dull, dreadfully, dreadfully boring compared to... this.

"This would be your 'why,'" he hears Mycroft sigh at his elbow, and then they're walking forwards in tandem toward the last cell at the very back of the room, and with every step Sherlock feels a new tremor in his hands as he itches to reach out and swallow the mystery whole, unravel all its secrets, cut it open and spread it out before him. Mycroft glances over, sighing again when he sees the look of appreciative hunger on his face. "Please do remember there's a human being involved."

He stares, unable to grasp exactly what he's seeing. "But what - what is it?"

"Wednesday, August 22nd, not far from Kandahar - Captain John Watson of the Fifth Northumberland Fusiliers, impeccable service record, army doctor, is shot during a firefight. Naturally, he's wounded. Or, as you can see," Mycroft grimaces, hand tightening on his umbrella, "not so naturally."

The man - John Watson, he amends mentally, stepping closer to the glass - is laid out on a white bed, black straps thick around his wrists and ankles where they're tied to the steel reinforcements. He's covered by crisp cotton sheets up to his waist, but his chest is bare, and from his shoulder...

Sherlock's breath is practically fogging the window pane. "No, what is  _that_?"

Seeping from the wound, a gaping hole that winds in chords around his injured arm and throws the veins around it into sharp relief, is blood, but it's not the dark, metallic grey you'd see from any normal cut or gash. It looks like...  _life_ , an infinitely brighter shade than anything he's ever seen before, and it oozes from a myriad of similar shades upon his chest, blending and bubbling and it's blood, but it's more, so much more, so vibrant and -

"Red," Mycroft says. He lets the word hang in the air between them, as it registers for the first time in Sherlock's ears. "He calls it red."

A trillion variations in this world, Sherlock recounts, as they stare down at the prone figure. Like the clinging, seething haze of static on a television screen. But there's finally something new.

 

 

**  
**

John Watson is sleeping, or fighting infection, or doing something ridiculously human and boring while something so very opposite happens to him, and though it makes him want to gnash his teeth with impatience and irritability it's an opportunity for Mycroft to take him into one of the adjacent cells and lay out the facts.

"Our scientists have tried everything, but as far as they can tell the chemical composition is the same. It's just -"

"Not black. Or white. Or grey or dust or magnolia or -"

"Yes," Mycroft interrupts, throwing him a hard glare over the table. "I'm aware of what it isn't. We just don't know what it is, or long-term effects and whether it's..." his lips pull down in distaste, as he probably imagines the mountain of paperwork and bureaucratic scandal that would arise from such a thing, "contagious."

An amused grunt falls from his lips. "Your top scientists have failed, and you're falling to me? Should I be touched or frightened?" In truth, he's neither, and he's more than aware that whatever this is likely does spread if the deserted hallways and lack of available scientific minds are anything to go by, which is why it's fallen to him. Sherlock, unremarkable, unimportant to governments or royalty or the world but for his brain. Spareable.

But unlike Mycroft, unlike the government, unlike most of the world, he's not concerned with the effects or consequences - why this matters, why this singular, strange case of one ordinary man is important;  _yes_ , the causes, those are far more intriguing than the dangers.

Mycroft seems to understand, in the way only he has even been irritatingly able to do, but shrugs his shoulders nonetheless. "It hardly matters to you, but -"

"Plebeian government scandal? Terrorist organizations harnessing this 'red' for foul purposes?" He lifts an eyebrow, Mycroft inclines his head, and Sherlock snorts again. "I'll take the case, but not for your reasons."

"Good. That hardly matters to me." Sherlock's eyes snap to Mycroft's, and they hold each other's gazes; in it he understands that his brother would sooner sacrifice Sherlock's safety than that of his precious, international peacekeeping, and that Sherlock would just as soon let him.

Mycroft breaks away as the intercom system at his elbow crackles to life. "Mr. Holmes?" a voice inquires. "The patient is awake and ready for transport."

"Thank you," he responds, and the blinking light goes dark. Sherlock is already rising, looking towards the door, but Mycroft leans across the table and when he grasps his brother's arm, there is a strange, filtered glass of emotion there, far removed from his usual orderly calm. It's what unsettles him most of all, strangely, and he steps backward, away from the touch. "You're the last hope. It's all up to you, now. Find out what it is, find out a cure, and don't get sidetracked."

Mycroft settles back against his seat, once again appearing collected as he rummages in his inner chest pocket. Of the two files inside, Sherlock catches glimpse of 'Roy' on another before it's cut off, but the one of interest has 'John H. Watson' scrawled along the edge. He takes it eagerly from his brother's careful grasp. "You are aware of the national significance of this. Should it get out, we may have anarchy on our hands."

Sherlock rifles quickly through its contents, scanning the letterheads of scientific experts and the titles of their findings before reaching the end. "No doubt," he surmises, folding it carefully into his coat.

"As a result, you're on a time limit."

"What?" he snarls, then, "How much time?"

"A week."

"A -" Sherlock doesn't bother to finish, grinding his teeth instead around the words as he thinks. "Fine. But all my testing, all my equipment - all of it happens at Baker Street. And Barts," he adds, after a moment of thought.

"If that is what you wish, it can be arranged."

Sherlock nods, and then makes for the door. "Anything else I should know?"

There's a long silence, and though he already has his fingers on the cool handle of the exit he turns back when Mycroft's reply isn't immediate. "Well?"

"It's a week," Mycroft says haltingly, "Because that's when the others began to see something called 'green.'"

Sherlock's fingers tremble. "There's more?"

"I'm sure if there is, you'll find it. Just - be careful. I won't let you go over-"

But his last words are swallowed in the sound of the door swinging shut behind his brother, and Mycroft sinks down into the hard, plastic chair and steeples his hands in front of his face, watching long after a sheet-covered John Watson is wheeled out of the room on a stretcher, Sherlock Holmes following just behind with a hand perched on the gurney, and the rooms outside go dark.

 

 

**  
**

When John first wakes up, it's to at least twenty people milling around in a cold, too-bright room, and all of them are talking and there are monitors beeping and it only becomes more chaotic when one of the women spots him blinking himself to wakefulness and screams. But then they're jabbing a needle in the crook of his elbow, he sees a flash of...  _something_ , something unexplained, but then it's gone and he's being pulled into the dark again.

The second time is no less disorienting, but it's definitely more quiet. As best he can tell he's on a sofa in some bloke's living room, and he knows it's some bloke because some bloke's eyes are currently about three centimeters away from his own.

"Bloody hell," he croaks, coming fully awake, flight or fight response prompting him to scramble backwards. He's met by the arm of the couch, and he huddles against it, rising up on his elbows, chest heaving and eyes wild. "What the fucking -"

The man sighs loudly enough for it to seem like an actual interruption. "Please don't force me to restrain you  _again_ ," he sighs, and as he steps back and John blinks him into focus he looks more like a petulant child than the adult planes of his face and bright eyes - thirties, maybe,  _barely_  - would lead him to believe.

He grits his teeth, temper quickly rising with the ebbing of his shock. "Look, mate, I-" he starts again, but a searing wave of heat and pain rockets through his shoulder, so intense he nearly doubles over. He gasps as it roils through his chest, seeming to diffuse after a few seconds of an agony he's never felt before. "Jesus Christ," he gasps when it's over, elbows collapsing beneath him as he goes flat again. He blinks a few times, clearing away the blur of pain, and when he does the man is standing over him, only this time with a small plastic cup in his hand.

"Here," he says without ceremony, forcibly taking his palm and curling two pills inside it. "I need you lucid - briefly, at least - if I'm to solve you in time."

John looks at the medicine warily, then back up at the man. "Solve me?" he asks with a derisive snort. "Am I some sort of mystery?"

One corner of what is really a peculiarly shaped mouth quirks upwards. "Yes." He abruptly darts away, John sluggishly tracking his progress over a cluttered living room, as the man pushes aside papers and books on a desk before holding aloft a white envelope, which he then returns to dump on his chest. A weak spasm shudders at the impact, but it's barely an echo of the agony of seconds before, so he counts it as a blessing. The man seats himself on the table, knees brushing up against the couch as he leans over them and peers down at John, once again uncomfortably close. John's not sure if he likes the look in his eyes, like this man is taking him apart from the inside out, as his curious, ghostly gaze zips across his form. The man, however, seems to like what he sees, as he settles back and flexes his palms over his knees.

"This should explain everything, as I can tell you're not likely to trust me until you have all the facts at your disposal," he says with an arch wave of his hand.

"You can tell?" John parrots, but it's true that he's already propping the file open and searching its contents.

"That, and everything else," Sherlock notes, tipping his head.

"You mean you read my file."

There's that smirk again. "No." His eyes focus in on John. "The file tells me all about your condition, but not about who you were before it made you special. But that's simple. I've been informed you were an army doctor in Afghanistan before being invalided home. But that was obvious from your hair cut, your tan line - none above the wrists, so abroad but not relaxing on a beach somewhere - and, yes, unit was obvious from the tags. But then there's your family life - you've got a sister, drinker, recently divorced her wife, probably because of the drinking, but she hasn't been around asking about you so it's unlikely you're close. No other relatives, very few contacts on your phone, so no extended family network."

"Brilliant," John whispers, and the both of them look taken aback.

The surprised expression flits across his face as if it's not used to being there before he launches back in. "But it's obvious you're a caring man; why else would you take the danger of attending to a wounded soldier when it obviously got you shot yourself? Ah, yes - charging into a firefight, easy enough to get shot from the front, but that's an exit wound on your chest. The entrance was from behind. So. You turned back for someone."

Hazy memories jump through John's mind, flitting across like a screen on rewind, too fast to catch. His hands are shaking. "Stop," he says, and then louder, "Stop, please." He takes a deep, shuddering breath, but it does nothing to calm him. "I don't know - you're right. You're right, and that's amazing, absolutely amazing, but I don't - what the hell..."

"Oh, do keep up, John," he sighs.

It's John's turn to scoff. "I've just woken up in some random, sodding flat with a random, sodding... genius who knows my whole life story, a fucking bullet hole in my shoulder, and you're telling me to 'keep up'?" He laughs bitterly. " I don't even know where we are, I don't even know your name. Tell it to me straight, or I swear I'll find a way around this shoulder to throttle you."

The other man's mouth snaps shut, and he looks almost amused, turning his gaze to John anew. It closes, slowly, and he inhales. When his head tilts he gets that look in his eye like he's dissecting him again, and John itches to draw the sheets and blankets up and secure them around his chest, but with an effort of will he remains with his stoic gaze trained on that arresting face.

"The name is Sherlock Holmes. This is 221b Baker Street. And you are John Watson, but you're more than that. You're a medical anomaly." He smiles, quick and sharp, but almost as quickly as it flashes across his face it's gone again. "And you're my subject, who is going to die if you don't do as I say and stop asking stupid questions." He jerks his head in the direction of the file and the plastic cup of pills. "You'll want to be taking those soon or the pain is going to get worse, and I can't have you passing out again."

John's still stuck on 'die', still half-dizzy with pain and and the last surges of adrenaline as they drain from his system, but he remembers his words -  _keep up_.

And though he has no idea what's going on, and though the man in front of him could be anyone, there's a strange form of sincerity to his exasperation and a weird... pull he can't describe. Out of all things, this Sherlock Holmes is the only one h can trust. Whoever he is. He's got nothing else to go on, so it has to be the best bet.

Plus the 'die' thing. That's really... not good.

"If this is poisoned, I will haunt this flat when I'm dead," he promises, and downs the pills. He straightens, and then turns to the man with his file outstretched. "Now tell me what's going on - Mr. Holmes"

One more curious, appraising look. "Sherlock, please." And Sherlock is launching into the tale.

When he finishes, they're both quiet, John taking in the information. "Can I see it?" he asks, strangely curious himself.

"They say you already have seen it. In fact, you were the first. Apparently you named it. This 'red'."

"I don't remember." His voice is hushed. Sherlock's told him everything - the firefight, the blood, the red. How he's gone and done something apparently magnificent rather than getting himself killed, though in this case he's not sure which is worse. He traces the edges of the bandage on his shoulder. Before he can think about it, and before Sherlock can say or do anything to the contrary, he tugs at the edges. The adhesive tape protests, and his flesh stings and comes away...  _red_.

Sherlock's at his side in seconds, jostling his own head for space as they peer down. Like normal blood, it's matted and drying at the edges as it clots, normal tissue threading around it. But it's not the typical, dark, black liquid that everyone else has. It's...

"Novel," Sherlock breathes, and probes at the edges.

John twinges. "Hey! Some warning would be marvelous," he grumbles, shoving his hand away. It reaches back persistently, and John slaps it, raising a look of affront to Sherlock's face. "Can you actually give me a second to look for myself first?" It's almost comical, how offended he looks, but John needs to see it for himself before he actually does get hysterical. Just take a minute to... process. Yeah, that's the word. Steeling himself, he looks down again, allowing his eyes to slip over the puckered edges of strained skin. And mostly, the weird, iridescent blood that surrounds it.

_Red_. Strangely, it sounds right in his head. It just... it isn't right. It can't be. There is black and white and all the hues and palettes you can make out of that, from Sherlock's ebony hair to his ivory skin, for instance. But that's it. That's always been it.

He leans back, and almost immediately Sherlock takes the opportunity to dive in instead. "I need to contact your superiors in the army," he says in passing, looking as if he desperately wants to touch but restraining himself nonetheless, a fact John's grateful of. "Find out what they can remember about the incident. Might have to excite the same conditions..." He whirls away, towards a cabinet where he quickly pulls from the depths a scarf and coat. Both are settled thickly around his shoulders before John sits up.

"And what do I do? Sit here and bleed?"

Sherlock smirks. "For now. Rest. Tomorrow, I'm going to find you a cure, and you're going to help."

John feels like he should protest, but he's getting groggy again, and his eyes stray towards the empty plastic cup. "You drugged me," he says, words sluggish.

"You only asked if it was poison," Sherlock responds, a little, uncomfortable jerk of his shoulders in some approximation of a guilty shrug, before it vanishes with the man disappearing down the stairs. He's left dazed and confused, the drugs working quickly, perhaps the whirling dervish of the man himself just leaving him that way as it is. John's eyes close around the image.

_Blue_ , he remembers vaguely, as he slips into a troubled sleep.  _The scarf is blue_.

 

 

**  
**

Sherlock is so intent on his microscope that even he nearly misses the sound of John edging into the kitchen. "You're awake," he mumurs appreciatively, eyes still glued to the slide. The footsteps stop. Shifting weight.  _Uncertainty_. He tempers his smile, straightens and turns to John - no, not uncertainty. Settling. Fighting stance.  _Readiness_.

Oh. It seems there's more unexpected about John than his blood. He tucks that away for later and stands fully, gesturing to the microscope. "A sample of your blood. Taken while you were asleep, didn't think you'd mind." His focus shifts again, back to the slide, and with one hand he gestures John over while the other taps restlessly on the tabletop. "Come and see."

He can feel John's hesitation, but he doesn't disappoint, and soon the man is peering over his shoulder at the monitor screen Sherlock has set up on his laptop. A few seconds pass. "Right, what am I supposed to be seeing?"

Sherlock looks incredulous, but with a heavy sigh he points toward the red cluster on the screen. "You're a medical doctor, you know a blood sample when you see one. Interesting antibodies present, but we'll assume those are a result of treating your wound. What's more interesting is the protein chemical, hemoglobin... it's an elemental Iron transport, but yours is red."

John nods, and Sherlock stares blankly. "Sorry, but I thought we already knew that?"

"John," Sherlock repeats softly, and lays a finger on the computer screen. "How would the computer know what red is? Why would it process the pigmentation?"

A light of understanding appears in his eyes. The red isn't just coming from him. "So, it's not just me. The red isn't my fault."

Sherlock huffs. "I don't know," he admits. "The computer didn't know red until your blood put it there. It's definitely connected to you, but it's not that you're unhealthy or different in any way. You're just... _seeing_  things differently." He pauses in his tapping. "Oh," he breathes, and whirls on John.

"I thought it was something in your blood, but if we're both seeing it; if the computer's seeing it -" he doesn't stop to finish his thought, instead marching past John to the counterspace. Shoving open a drawer, Sherlock rummages inside until he turns back around, brandishing a blade. John raises his eyebrows. His glance falls to the knife, then rises again. He sighs. "Do relax. I am trying to help you," he says, and sinks the tip into his palm, drawing a thin line across the flesh. It splits along the edges, fine, fraying skin pulling back to reveal -

Blood.

_Red_  blood.

His smile threatens to split his face as the liquid - clear, bright, beautiful - wells up from his skin. "Gorgeous." His thumb presses down into his palm; the blood spills faster, coating his hand, welling in the lines of his skin sticky and hot and alive and so, so red, like a sea of life for his hungry, searching eyes to swallow.

"Does it scare you?"

John's voice comes soft and quiet. Sherlock had almost forgotten he was there. Looking up at last and his line of sight falls to John's hands on the knife, where his own eyes are trained on the slick line of red at the shiny point of the metal. One of John's fingers, just the tip, reaches out to stroke along the sharp, contoured head, and Sherlock, though always on constant awareness, is suddenly, acutely, hyper-aware of John - not in the sense of his proximity, but for the first time of his strangeness, of his novelty, the way he looks dispassionately at the knife and then drags his eyes back up to Sherlock and  _oh, that's new_.

"No. Not in the slightest."

He reaches for the gauze - only to be met first with John, shaking his head and sighing, "They've put me in the care of a madman." John takes his wrist and presses the edges of a plaster down around the open cut, his thumb stroking along the center to secure it. Once, necessary. Twice - extravagantly  _not_.

"Does that scare you?" Sherlock inquires, voice low, and the gentle pressure on his skin hesitates.

"No," comes the answer at last, honest if brief. "Now are you going to tell me what's going on?" Sherlock flexes his fingers and breathes again, both of them drawing back, and he turns his focus to the blade and the spot of red still stubbornly clinging to the tip.

"Think, John," he says, and his eyes are already far-off, probably looking back through that great, bloody brain of his and speculating away. "You were the only one who had the red. We don't know why, but we know that you saw it. And then others started seeing it. Then I saw it, and now my blood is red."

John pauses. "Infection?"

Sherlock nods shortly. "It's a possibility. I need more data. More people who have seen it." At John's second curious look, he sighs. "I've followed procedure to a tee," he says, his lips curling around 'procedure' like it's a dirty word. "There's no reason why infection would pass between us, unless airborne or passed by sight. Computers don't breathe, but they can process information. How do humans process information? Sight."

A second pause. "I've never heard anything so ridiculous," John snorts derisively, but his laughter is nervous. Sherlock, now fixated again on the slide, pauses long enough to give him his own glare of derision. John continues to splutter. "What? An infection passed by sight? What does that even -"

"John. Open your mind. We're not dealing with ordinary and mundane. This is the realm of the impossible. Or, if you prefer, the improbable."

John holds his hard gaze for a long, charged moment before it drops with his shoulders. Expelling a sigh, the hand attached to his uninjured arm rises to his face, rubbing at the furrow between his eyebrows, and Sherlock knows he's won. "Fine. What's next then?"

By now he should expect to be surprised by John Watson, but his whole body goes through another freeze at the words. "You actually want to help?" he says, processing slowly. He turns, still slow, and advances on John in steady strides, peering down at him curiously. The man doesn't shrink, doesn't back away for an instant, but rather straightens and returns his level gaze. Despite his injury, both hands clench into fists at his side, and his spine goes stiff. Solid. Dependable. But as his eyes travel freely over his frame, assessing, assessing, assessing, it's clear that there's a danger there, too, a danger he knows well. A hunger, an addiction.

"We don't know how far this will go," he says when John doesn't answer immediately. "And I don't know if there's a cure waiting for you at the end. You might die from it. In the chance that you don't, you will be hunted, either out of fear or out of desire for what you have that no one else does." His eyes dart back to John's.

Still no response.

"Could be dangerous."

John blinks up at him steadily. Then, "I started this," he says, head nodding up and down, almost thinking aloud. "I don't know how. I don't know why. But somehow I'm responsible, for better or for worse. And you're the only way to fixing that, or finding out how to stop it. I think I'll take my chances. So I'll repeat - what's next?"

Sherlock smirks, and then it falls from his face just as quickly. "John," he breathes, and steps even closer, the space between them diminishing to a bare few centimeters as Sherlock's shadow falls across his face, breath fast across his cheek. John leans back, confusion coloring his face.

"What?"

"Your eyes." He breathes the words like a prayer. With a so far unseen delicacy he reaches out and grips John's shoulders, turning him into the living room. He points him at the mirror. "Look."

John does, and nearly chokes on his next inhale. Blue, blue, and he'd forgotten about the scarf but there it is again staring back at him from his own eyes, impossibly dark and varied and it's so different from the red, almost opposite in how deep and light it is, all at once. Where the red is rich and vibrant, the blue is calm and manifold, like layers, and it's -

"Blue," John manages. "It's called blue."

"Beautiful," Sherlock murmurs from over his shoulder, and John can only nod in response, the both of them staring for longer than they know, watching their reflections stare back, and the piercing blue reflected within.

 

 

**  
**

In a taxi on the way to St. Bart's Hospital, where Sherlock had waved a hand and basically told him he'd been able to pull strings for equipment, Sherlock fills him in on the missed details.

"I did search for your superiors, or anyone related to the first incident. Nothing." He frowns, watching but not seeing as the streets of London flash by. "Even the doctors who treated you have disappeared. No records, either. I'll have to ask Mycroft."

"Mycroft?" John questions. His hand pushes the sunglasses obscuring his eyes higher on his face, eyebrows going confused over top of them.

Sherlock takes in air like it's an actual, physical effort of the Herculean sort. "My brother. Responsible for my involvement. The only reason you're probably still alive."

"Guess I'll have to thank him for -"

"Oh, please, don't; no need for his ego to become as large as he is," Sherlock says, and John's eyebrows now lift at the unexpected sharpness of his tone. Despite himself, he smiles, settling back into the seat.

"Sibling rivalry, interesting," he muses, smug with his own deductions, and from the corner of his eye he sees Sherlock shoot him a look usually reserved for gum found on the bottom of one's shoe. But that's all the response or information he gets, and Sherlock returns with a haughty stare to watch the blurred greys of the city out the window. John resists the unexpected urge to hum the whole way there.

When they arrive at the hospital, Sherlock immediately sets to work, throwing himself down the aisles of an empty office and breaking out diagrams and dusty, absolutely ancient encyclopedias from the medical shelves, on neuroscience and human optics and perception, things even John with his not-entirely modest medical education finds difficult to decipher. But when Sherlock turns around with his giant stack of books it's to plop them down unceremoniously in front of him with a pleasant, and even he can tell, entirely false, grin. He glowers.

"And what are you going to do?" he demands as Sherlock glides toward the doors, big, flashy coat making quite the unnecessarily dramatic scene as it swirls in a fervor about his knees.

"I need an eye," he says cryptically, and he's completely disappeared down the cold white hallway before John can do more but groan a protest. Well. Nothing for it, then. He eyes the stack of volumes with apprehension and some exasperation - he doesn't even know what's he's supposed to be reading up on, for god's sake - but at last a weary hand reaches out and grasps a medical journal from the top and props it open.

He then almost drops it in shock. He quickly turns to look at the bookjacket again, and it's back to a staple Gravel shade, but for a moment, he thought he saw... a sort of...  _bloom_  of color, like the book was red, too. Like it was meant to be red.

This time he actually lays the book on the table, rubbing his eyes tiredly.

It strikes him, then, how quickly all this has happened - ordinary Doctor John Watson, just another soldier with a bit of medical training, and then a bullet in his shoulder changed everything. And even that wasn't the end of it, because no sooner had he woken up in Some Random Bloke's flat than he was entrusting all his safety, all his care, to the very same Random Bloke.

Granted, he's extraordinary, but it's a bit odd that a day after lying in a hospital bed with no knowledge of Sherlock Holmes, he's now become central to his life. How central... well. Time would tell. Though what would happen if they did manage to solve it, if the new color did go away, he's not sure. Can't go back to the army. Would have to be doctoring, then, if he wanted to stay in London. Back to the ordinary. The second the thought has left his brain it's replaced by an odd sense of... loss.

But he doesn't have time to wonder about anymore of that, thank God, because then Sherlock is flying into the room, practically alight with excitement, and the door almost slams behind him on a tiny young woman struggling through with a large metal box.

"Sherlock," he says, reproach in his voice as he moves to help her, propping open the door. She shoots him a nervous smile, turning questioning eyes to Sherlock, who has chosen to ignore John's obvious call for apology and is instead breaking out a packet of medical instruments and laying them neatly by an examination table.

"Nice shades," she chuckles to John, who laughs. Christ, he'd forgotten they were there. He opens his mouth, searching for a reply - but stops short. Her mouse grey hair is now lighter, reddish, but not; something even newer...

"Hurry up," Sherlock interrupts loudly, to where they're paused in the doorway, and she starts into action, giving John another tight smile over her shoulder as she deposits the case on the gurney. John blinks, files it away to tell Sherlock later, and follows her.

"Who's this, then?" she asks as she approaches, and then, turning, thinks the better of it and questions John instead. "You a... friend, of Sherlock's?"

"Ah," he starts, awkwardly, not much knowing how to answer that, and Sherlock saves him the trouble of answering by unlatching the case and making a noise of glee that borders on obscene.

"A perfect specimen. Molly, scalpel," he demands, and she purses her lips but does as asked. John's forehead creases, and he decides to step in.

"Um, I can take it from here. I'm sure you've got work," he says, smiling gently, and she looks grateful even as she seems to look for Sherlock's confirmation. He, however, is engrossed in the severed head he's just lifted out of the case - which John now recognizes as some sort of organ transport freezer - staring hard into its eyes with the fixation of a lover. John grimaces at  _that_ particular image, and puts a hand on Molly's shoulder, to which she at last gives a bob and a nod and hurries from the room, one last curious look left behind as the door swings shut for the last time. Behind her, her and her  _hair_.

"You're a real charmer," John says, when the poor girl's safely out of the room. "Bet your girlfriends love being ordered about all the time."

"Girlfriends?" Sherlock murmurs, tilting the head back and probing at its eyelids, while the other hand gestures at a fine-edged blade just in front of John. "Not really my area."

John nearly slices Sherlock's hand off. "Oh. Right," he says when he's sufficiently recovered, and the sharp object is held in a palm rather than embedded in one. "Boyfriends, sorry."

It's Sherlock's turn to pause, and he uses the moment to lift a sardonic eyebrow. "Married to my work, actually," he says breezily, and though seconds before the air around them had felt uncomfortably thick and awkward, now it's all diffusing out in the small, teasing grin that dares to peek out around his focused expression.

John laughs, mostly at the oddness of this man but in no small part out of relief, but he does take a moment to add, gently, "That is fine, though. All fine."

His grin softens, just a hint now at the edges of his lips. "Thank you," he says, and then his face transforms, as out of his fine incisions he carefully lifts an extracted eyeball, gleaming palely in the low overhead lights of the laboratory. "Three slides. Please," he tacks on, an afterthought, and John acquiesces with a private grin. He watches as Sherlock cuts a thin slice of the retina and places it on the slide, following suit with the other two, and then seals them off with their thin glass covers. Finished and obviously pleased with his work, he rises from his concentrated stance. "Bag them. Find anything in your reading?" He lifts the cadaver's head smoothly back into the crate and shuts it, snapping off his gloves and depositing them in the rubbish bin.

"I didn't do much reading," John admits as he does as asked, jamming the bag into his pocket and turning back around. "I don't know what the hell you're looking for, to be honest."

"Anything about vision, how we process light; it's not a difficult leap."

John huffs. "Well, hey, for starters - I'm seeing more of it."

That catches Sherlock's attention. "More red? More blue?"

John tips his head. "That, and other colors. Molly's hair... brown," he tries, and then more certainly, "Brown. It's... it's like it's blooming everywhere, I can see it just at the edges, everywhere..." He closes his eyes again, and there it is, just dull spots of something amidst the enduring black. But it's  _something_. He rubs his temples, sighs.

When he opens his eyes again, Sherlock is watching intently. But all he says is, "We can do more reading and tests at home, I'm certain I have similar journals on the subject. Come on," he finishes, and John's nearly left behind as he sweeps out the door, metal box held in his arms.

He just as nearly crashes into his back attempting to reel after him. "Sherlock, what -"

"John," he says, and though it's soft, there's a sharpness to his tone that has John's senses immediately on alert, a quick surge he remembers from days on the battlefield. He looks around the blockade of detective to see two suited figures a few paces ahead, and the pulsing through his blood intensifies. Unconsciously, he moves more to Sherlock's side, shifting his weight back and angling to mirror the opposite pair. His fingers flex, his toes curl in his boots.

"Mr. Holmes," says one of them at last, voice rough and obscured. John looks to see if Sherlock recognizes the speaker, but his only reaction is a slight narrowing of his eyes. John looks back down the hall, jaw tight. "You have something we need."

_Me_ , John understands. Sherlock told him the rules of the game they were playing, only now they're actually on the field. The shiver of excitement, of the beginnings of that coiling, cold fear, are deliciously welcome as they pull in his gut; moreso is his knowledge of his ability. His certainty in that moment - equally cold, equally right - of what he is capable of.

Sherlock arches an eyebrow. "Do I? Now would that be a margin of intelligence, or something else?"

John's sure he should be disapproving of the way Sherlock eggs them on, but he ends up fighting to control his grin while the other two shift, anger humming in the air around them. "He's more valuable than you know," says the other, broad shoulders nearly blocking the flickering light as he steps forward one cautious step. "People are starting to... hear things. Serious people."

"We're not going to be the only people on your tail, soon." His smirk deepens into what could only pass in hell for a winning smile. "Give us John Watson, and you can go back to your science equipment and pretend none of this ever happened."

Next to him, Sherlock stills, and for a moment John wonders - but that sense of dread is immediately, intensely followed by the sense of  _Sherlock's_  capability as well. Because while he looks considering the fingers of his right hand are on the latches of the case, quiet, deft, while the others just brush against John's wrist at his side, a warning, a sign, and then he's fixing the thugs with another of those shiny, plastic grins.

"Hmm... how about a trade?" And then he flings the case forward.

As if the large, steel object flying at his face wasn't enough, the hinges Sherlock had cleverly slipped open come completely free during flight, and the head with its singular, unseeing eye, in place of the other a gaping hole, comes flying at the man as well. The moment of shock at that particular image is enough time for John to ram his good shoulder into the side of the first suit, sending him sprawling in seconds, while Sherlock takes the opportunity to hook a leg through those of the other and take him down as well. It's almost pitifully easy, and John only has time to reel back around on his momentum to see them on the floor in a heap, the severed head of that poor bastard lolling off to the side, before Sherlock is leaping over them - that ridiculous coat still dramatically askew - taking his hand, twisting him around again, and dragging them both down the hall at a flat-out run.

"That man's head," he pants as he's pulled viciously around a corner, snug against Sherlock's side as he peers down ahead of them.

"What about it?" Then they're running again, the way decidedly clear enough, though several orderlies peek out of their doors in curiosity as they whiz down the darkened halls. It reminds John oddly of nightmares he'd had as a med student of being late for finals and never being able to find the right classroom, or being assaulted by the cadaver supply instead. A bit different, this.

John shakes those thoughts off, refocusing on his words and his feet eating up the ground beneath him. "We can't just leave it there."

"Why not?"

"It's... that's... wrong!" It feels disrespectful, especially since he'd been so much help in the getaway. John is starting to feel bad for the poor man.

"He's dead, John," Sherlock comments idly, and then shoves him down another passage, the hallway yawning into a lobby space. He can see the iron-grey of dusk outside the doors that appear before them.

_Christ. Barely a full, cognizant day with this man and look where I am_.

"Yeah, yeah. That's a good point. God, and we're not. We're not dead yet!"

And then before he knows it he's laughing like a loon, laughing as they stumble out into the half-light and into a cab amidst the dense urban scrawl of a city awakening with the night, and he's not sure what's happening to him but he's willing to bet it'll be worth it in the end, especially when a quick glance at his side proves a smile on Sherlock's face that is as real as they come, and more than when he, too, starts to laugh.

 

 

**  
**

They arrive back at the flat, still riding their adrenaline high and giggling like schoolboys. It's odd, for Sherlock - not in the sense that he's enjoying it; he always enjoys cases, especially these ones, where the mystery is so thick he's practically drowning in it; can taste the palpable, ashen airs of the unknown all the way down in his lungs. But to be enjoying it at someone else's side, to be accompanied and complimented and lavished in praise - that's new. He's never needed it. Still doesn't. But sneaking a glance sideways at John Watson, he finds himself starting to... like it.

In the moment he'd just barely sidled his skin against John's hand, in that bare second of touch, there had been a wealth of communication going entirely unspoken, John responding like an extension of his nervous system as they reacted in time. And even his brain is struggling to wrap itself around what that means.

John Watson had come to him a mystery, but Sherlock's just now beginning to realize this is twofold.

He tucks away the second for later, the weight of the slides in the bag he'd taken back from John still heavy in his pocket, and ascends the stairs, flipping out his phone at the top.

"Mycroft," he says, soon as his brother answers. "We were attacked at Barts. I doubt you'll have anything to do with that?"

He can hear him conferring quietly with someone on the other end and waits with impatience until his brother clears his throat. "We're looking into it."

Sherlock hums under his breath. Behind him, he can hear John moving into the kitchen. Sherlock tries to remember where he'd put the tea last and dismisses it. Mrs. Hudson could just make it for them. He returns to the conversation at hand. "I need the retinas of someone who has seen it."

"I don't volunteer," he says dryly.

"Don't be obtuse."

Clearly anticipating a barb about his weight, Mycroft avoids further comment. "Well, it is to your advantage that one of the nurses working with John Watson suffered an unfortunate heart attack yesterday evening. I would pray it's not a fate that will befall us all, considering we've had to put everyone in hiding to keep them quiet. Bureaucratic nightmare," he sighs. Sherlock blinks as the realization strikes - ah, that explains why he couldn't get through to interview any superiors. But Mycroft interrupts his epiphany with a smug, "Though John seems to be doing well enough himself."

As he speaks there's a muffled cry and the crashing sound of several pans from the kitchen. Sherlock winces, and John stalks into the room.

"There's a -" he says, pointing behind him, strangely calm though he's looking at Sherlock with new concern. "A... thing. A  _certain_  thing in the fridge."

"It's not mine," he says shortly, "if that's what you're worried about."

"Not yours - Sherlock. You keep body parts where there's food."

"Well, where else should it go?" He folds his arms across his chest, looking petulant as he sinks back into the cushions and refuses, absolutely refuses to acknowledge Mycroft's amused snort on the other end of the line.

The kettle calls a sighing John back into the kitchen before he can give voice to any number of the things he imagines are clearly wrong with that response, and Sherlock levels his glare at the phone, as if Mycroft can feel it across the wires. "You were saying?" he intones, a voice that drips like icicles.

"Oh, yes, I was," Mycroft murmurs smoothly. "If you need a specimen, we have one, but one is all you're getting."

Sherlock nods, mind already racing ahead. "Sufficient. Have the eyes sent to me at once." He stands, intending to shut the phone, but Mycroft speaks first.

"Interesting, that soldier fellow." He seems as if he's about to say more, but just clears his throat again and says, "Good day, Sherlock." The other end clicks and the dial tone fills his ears.

John putters aimlessly about the flat for some time. He doesn't want to disturb Sherlock where he's bent over a microscope and lost to the world, but he's feeling useless. He tries the medical journals for a bit, but it's nothing they don't already know about eyesight. Even the internet is uninformative - there are no recorded instances of anything like what's been happening to him, from searches of blindness to mental illness. Definitely nothing so epidemic. It just leaves him feeling disheartened, Sherlock frustrated as he flounces back to his precious eyeballs, and the flat steeped in some sense of... unease.

Worse, and he's not sure whether or not to tell Sherlock yet, but he's seeing it more and more often. It's like it's bleeding from the edges of his sight itself, where once it was just in the blood. Now he turns, and at the corner of his vision the arm of the chair is  _burgundy_ ; he shifts, the mug in his hands is  _olive_ ; the fire burns  _orange_  and  _yellow_  and  _blue_  at the center and - he

does a double-take, looks back, and all the normal shades of chrome and iron remain.

It's like memories, distant and once-loved, that crawl across his vision before disappearing back into the haze, leaving the gaping sense of something lost. Absent.

And then, sometimes, they stay. Like the red of the blood or the blue of John's eyes and Sherlock's scarf, they're creeping in from an unknown world of vibrant shades and dangerous vitality, lost between the universes and sticking to the things they touch. It spreads like a virus, there is more and more blue, more and even more red; now the green begins to touch on John's jacket and the warped glass of the doors between living room and kitchen and it is as if a swarm of insects is crawling across the surface of all these common things to leave them buzzing with it, burning with it, alive with it.

"John. John."

Someone is shaking him. John starts, head coming up from between his knees with a gasp, and he nearly cracks Sherlock's jaw on the way up. "Sorry," he pants. He's still in his chair, but the fire has long since settled to ash in the grate, and now Sherlock is crouched before him.

He's eyeing him critically, and it almost looks like concern, uncomfortable and disused on his face, but when John peers closer himself the look goes clinical and detached. "It's getting worse," he says, more statement than question, but John nods anyway. Then, strangely, he laughs, and at Sherlock's second questioning look he can only shrug, eyes catching and mouth going slightly slack because -

"That's just it though," he breathes, refusing to look away. Sherlock's eyes have gone... gone... well, he's not sure what, really, but they're...  _Christ..._  "I'm not sure it is worse. There's something... beautiful about it. I'm seeing things in this whole new light, and it's -"

"You must stay unbiased. Remember, we don't know a thing about effects or possible dangers to your health. Don't grow attached to the subject."

John's gaze hardens. He draws himself up, leaning forward on his knees. It only puts him closer to Sherlock's gaze, which is really starting to throw him off, but he stands by his annoyance with determination. "And cooing about how marvelous it is every time I name a new color, that's not becoming too attached, then?"

"I don't coo," Sherlock says, outrage palpable. "There's just -"

"No, you do love this, don't deny it," John snaps back, but his face gentles. "You have to understand what it's like. You're seeing it." He pauses. "Sherlock, your eyes have gone all... colory."

"And is that the clinical term?"

"Oi, you, shut up - this is what I'm talking about." He exhales. "Christ, your eyes..."

Sherlock shivers slightly, whether at his tone or his words John can't tell, but he looks decidedly more rapt when he whispers, "Tell me."

The request is odd, but in the scheme of things, in light of the day they've just had, it's almost natural. Especially from this man, so odd and incredible himself. And especially when it's as if his eyes are telling that same incredible story. A myriad of things, of color, all swirling and swollen together, and he notices the contrast now more than ever.

"They're almost grey, still," he tries, voice gaining speed as he gives voice to this confession of what is either illness or glory and yet remains shrouded in a treasured mystery whose weight can hardly be guessed. "Almost like a mercury. But you tilt your head, just so," his fingers brush along Sherlock's jaw, thumbs rasping over the junction of his throat as they slide away, neck now bared, "and they're this green, like... like the ocean on a cloudy day." His hands push Sherlock's chin up, brushing just against the underside, where John can feel he hasn't had time to shave, can feel the pulse  _red blood red bloodred_  of his carotid. "And now blue, blue as an autumn sky above the city." The words are barely there, hovering just over lips that John belatedly, hazily realizes are angled just so, just perfectly that if John were to only shift his weight they'd meet his own, his cupped hands over Sherlock's neck drawing him closer like a thief holding a precious stone. And god, does John  _want_ , in that moment, to  _take_...

"John. I have a question."

As his breath fans over Sherlock's open mouth, as he can smell nothing but him and what he doesn't doubt is a hideously expensive cologne, as his fingers quake in the curling hair around the nape of his neck, he trembles on the edge of a cliff-face with the effort of a simple, "Mmm?"

Sherlock speaks, his voice low and rough. "How do you know what color the ocean is on a cloudy day?"

John draws back, eyes lazily shifting back into focus on Sherlock's face. "Oh," he states, and then as it fully registers, " _Oh_."

John's bewildered enough by the realization that he has to remain sitting in the armchair while Sherlock is already leaping up and about, postulating entire systems of theories under his breath as he bangs around the kitchen. He almost doesn't hear Sherlock questioning him again, and it's only after more exasperated calling that he shakes himself out of it. "Sorry, sorry, it's just a lot to take in; give us a minute."

_All those colors, all those unnamed creations, just waiting to fill the world - imagine all the artists, all the paint, spilling into the seas and over sidewalks and sand, blooms of it, swathes of it, until the world is bathed in it, as it has always been meant to be. As it has always been meant to be._

_Meant to be._

Sherlock scowls, for once oblivious to his private plight. "We don't  _have_  a minute. You've basically just told me everything has a natural color, is that right?" John shrugs, Sherlock's eyes narrow in response, only producing another helpless shrug and more narrowing of eyes until John stands and gestures into the empty air of the living room instead.

"What do you want me to say? I don't know any of this, Sherlock. Yes, that's what it seems like, but it just sort of... came to me. In the moment."

Sherlock pauses, confusion creasing his forehead. "Do you want me to recreate the moment?" He steps closer, arms rising to John's arms as he leans down, those damn eyes intent and hypnotizing.

John coughs, tactful hands coming to his chest and applying a gentle pressure. "No, uh, thank you, don't think that's going to work," he says, firmly, viciously hoping he's not being mocked - though he probably is, that body-part-keeping bastard. Christ, even the voice in his head is already fond. He clears his throat again, fighting embarrassment, and dares to look up. "I just mean - I'm tired." And he is. The words being shaped only makes him feel it more intensely. It's all a little more than overwhelming, this, and now there's even more to think about, even more spilling out of his brain and  _Jesus_ , is this what Sherlock feels like all the time?

He rubs his shoulder, sighing, wincing a little as he works at unseen knots. "You can't keep pressing me for answers to questions that have never, ever been posed before. I just don't know. We're not all geniuses. And us normal people need time to process. Don't you ever sleep? Or eat? I don't think I've seen you do either since this whole thing started." He rolls his shoulder back, meanwhile looking to Sherlock for confirmation of what he already suspects.

Sherlock snorts. "Tedious. And definitely not on cases."

John stops and gapes, realizes what he's doing, and hurriedly shuts his mouth. "Well, I can't be the one to judge. But if you're looking like a zombie in the morning I will personally shove a piece of toast down your throat, and I mean it."

Despite himself, Sherlock's looking amused, until he seems to latch on to something of what John just said and it turns into a deep frown instead. "'In the morning'? You mean you're going to bed when there's finally something fun happening?"

"Not a genius, remember?" He glares in warning before Sherlock's open mouth can make a comment. "For me, this isn't the fun bit. I need sleep. I need time. Besides, you don't need me right now -"

"Of course I need you."

They stop.

"I don't -"

"I just meant -"

"Thank you." John is well and truly touched, and it's made all the more pleasant by how affronted Sherlock looks at himself for the words, as if they'd made it to the air of their own volition. But he deigns to nod, curtly, before spinning back to the table.

"There's a bedroom upstairs. I'll wake you with any interesting developments."

John smiles, hoping they have the same definition under the heading of 'interesting' but risks not mentioning it. "'Kay. Goodnight, Sherlock."

"The infected sample should be here shortly. I can make the comparisons and let you know what I find."

"Sounds good. Goodnight, Sh-"

"I'm confident tomorrow we'll find the source, and then we can start looking for a cure."

"Sherlock." He turns back to the kitchen, propping a hand loudly on the doorframe, and Sherlock looks up in surprise. John arches an eyebrow. "Anything else before I finally make it to the bedroom, hm? All out now, last chance."

Sherlock hesitates. "Sometimes when I'm thinking I play the violin. I can go days without talking. Or eating, or sleeping. You've seen how I keep my experiments all about the flat, so that's the worst of it."

John blinks.

"You'll be looking for a flatshare when this is over. I think I'd like it if you stayed. If you, of course, are amenable."

John blinks again, but there's a small smile under it, looking at Sherlock fidgeting with the dial adjusters on the side, his shoulders tensed in a way that makes it abundantly clear this isn't a conversation he's had often, or anything he's ever felt before. That fond sensation, of being touched, of an unexpected comradeship found in the most unlikely of places, doubles, swelling in his chest without warning. Potential kisses notwithstanding, there's something there. And that's enough.

He dips his head. "Good _night_ , Sherlock," he says, and then disappears up the stairs. Sherlock wastes no time in staring after him, instead busily noting all the remarkable aspects of each retinal slide in a journal on the table, but John thinks that as he shuts the door with a quiet click, an equally soft, far more wondrous chuckle drifts up from the kitchen before all lapses once more into silence.

It's what he thinks about as he drifts into sleep. But later in his uneasy dreams are blooms of color and a translucent-skinned Sherlock standing naked in the ocean, beckoning him forwards, pointing to a horizon mottled with the purple and orange and yellow of a brilliant and magnificent sunset, and in the distance the common, detestable black of a gathering storm. He takes Sherlock's hand as it hits, a bolt of frigid white-hot lightning, and wakes with a start.

 

 

**  
**

_Slide #1 - Retina of Uninfected Mammalian Specimen_

_Nervous tissue_

_1000x - Retinal Ganglion Cells._

_Subretinal space; photoreceptor cells._

Low resolution, fuzzy and hazed as compared to the electron microscope at Barts, but it's there. He'd spent the day analyzing the slide, drinking in the strained image of criss-crossing lines, eyes immediately latching into the pattern - thin stripes, rods of black against the white, parading in from both sides in a single column. It ropes across the viewfinder like a barcode. He'd snapped a photo as well, but it was more for record's sake than his own - it still hovers across the back of his eyelids when he blinks, obvious, remembered.  _File, save._

Carefully, now, he removes the first slide and replaces it with the second, securing the tiny silver clasps and re-checking his light source.

_Slide #2 - Retina of Infected Mammalian Specimen_

One of Mycroft's personal assistants had brought it over in the early hours, as promised. Obviously eager for progress. But those concerns are irrelevant now compared to this; Mycroft barely warrants a second thought as he peers closer.

_Nervous tissue, 1000x - subretinal space; photoreceptor cells._

He is huddled around the device like a miser about his treasures, jealous of any who would infringe upon this precious thing that, in this moment, in this discovery, is his and his alone.

There is no breath of wonder at the realization when it comes. There is no shocked exclamation. In stride, a scientist, he takes down what he sees, noting his observations as cool and compartmentalized as ever. He breathes deeply, evenly. He blinks slowly around the image and its differences that will change the world.

He nearly snaps his pencil in half when John speaks up from the stillness, voice rough with tiredness and recent sleep, "Anything yet?"

He expels one long, low breath. "Everything. Come and see."

As he listens to John shuffle closer, he begins to explain, fingers almost reverently stroking the sheafs of notes and slides before him. "The uninfected sample was typical to other retinal scans; common ones found in your medical textbooks, I'd imagine. Pigment epithelium followed by a column of rod-shaped photoreceptor neurons.

"But in the other sample, from the nurse who'd seen the red and reportedly began to see 'stirrings of exotic visual flashes,'" he quotes from a file, skeptical eyebrow raised as he adds instead, "most likely traces of blue and green, based on our progression - ah, yes," he sighs again, now reaching for the slide labelled #2 and setting it once more into the clasps. "The rods are there, but there's something else between them. More... tapered, conical. And they're absolutely everywhere in the fovea. For central vision," he clarifies, "essentially meaning they're in focus and we're actually seeing colors with more clarity than anything we've ever seen before in black and white."

He has to take another moment as he adjusts the microscope for John to see, but more to temper the icy excitement that thrills along his spine, sharp and alive with exploration and success. "I still have no idea what it means, but I've found the difference. It's there, and it's real. It's the beginning. I'll have to talk to an expert, but at least it's a start, and then we can work on a..." he trails off, as through that crackling forcefield of his own success, John sparks into focus.

Shifting slightly, he watches John lean in. More than watching, he's an observer by trade, and in the shadowed folds beneath his eyes and the stiffness of his shoulders he can read fatigue, in the crease between his brows is worry, in the steps forward he takes despite this are hope and resolve. But something else, something else makes itself apparent, pressing in on John from all sides as heavily as if he'd been wearing it - it's nervous jerks of his head, rapid, flickering glances from all sides, restless and tense in posture and tapping fingers. In all their (albeit short) time together, and not once has John appeared so uncertain and at once so fierce. And so... unwell.

He straightens, and sways. Sherlock's barely out of his chair before John is stumbling backwards into the boundaries of his arms, thudding against his chest and hot and sweaty against him. "John?" he questions, voice curiously high as an urgent hand reaches up to palm his forehead, and another reads his pulse where it's curled about his wrist. Not particularly warm, and the rate isn't high, so not sickness (which would have turned this miracle infinitely more sinister) - but John certainly _looks_  ill, dizzy and gasping as, with Sherlock's assistance, he sinks to the floor. His eyes are squeezed tightly closed.

"Oh, god, Sherlock," he wheezes, clinging hands fisted in his shirt - now some form of  _purple_ , an unknown sense of  _aubergine_  filling his head with visions of eggplants that are distracting and thus viciously shooed away. He has a worse problem, now, because John is still twisting, face contorted and glorious  _cerulean blue_  eyes still clamped shut. John's pain, obvious in those moments of his helpless standing by, feels like it physically unfolds under his sternum as well, and he registers empathy with a shock that would be more prominent were he not otherwise engaged. It's not often, not often at all someone touches him like this - and now that same man is hurting and he doesn't know what to do and he can't stop it.

"John, you have to tell me what's wrong," he pleads, voice steady even as his hands are shaking where they're kneading John's upper arms. "You have to tell me so I can-"

"It's everywhere," he gasps, and his hands pull Sherlock closer. "I open my eyes and it's like the world is exploding." Another shaky breath, his head rocking forwards to rest on Sherlock's shoulder, sweat prickling on his neck where their skin touches. "Throwing itself at me, all at once, everything -" Abruptly his eyes snap open, wide as saucers, and they wildly roam the room before coming back to rove his face instead, hungry and bright before they're closed just as quickly; as if Sherlock had imagined the uninhibited life in those blue, blue eyes. "It's... beautiful, fucking hell; it's like it was meant to be this way. Like the world is supposed to be this bright all the time. But it's so much so fast, it's too much; Sherlock..."

His own words seem to have talked him down. He's calmer, his chest not rising and falling quite so heavily, and the sweat seems to have cooled somewhat after moments of the following silence, but he still has his eyes pressed into the junction between neck and shoulder, refusing to rise. Sherlock cradles the back of his head, awkwardly at first, but gradually relaxing, his uncertain fingers on the crest of John's scalp smoothing and taking the time instead to catalogue the strands as they go blond before his very eyes.

"That's what it was like in my head," he says at last. "All the time. Before I had a functional file system. And sometimes still, when there's too much outside. Too much..." He looks around, as if the words will appear in the air before him. But it's just his kitchen, just vague colors slowly invading from all sides.  _Just like he said_. He quickly retreats to staring only at John, by now colors that are familiar and warm instead of vicious and...

"Sensory overload?" John supplies, voice muffled.

Sherlock's mouth twitches upwards. "Yes, I suppose that's a term for it." He goes quiet again, ruminative. His fingers continue to steal over John's scalp, repetitive motions that seem to soothe him down again, until at last John leans back, and through slits of his eyes is able to fasten his vision on Sherlock.

"I could grow used to it, though. I could grow used to this." He reaches up, hand curving over Sherlock's cheek, stroking, thoughtful, before it falls and his eyes open bravely. "Sherlock," he says, and it sounds like the beginning of a question as he sits taller, and perhaps Sherlock would be more prepared for what follows if he wasn't still hesitating over the faint brush of calloused fingers on his skin. "What if I told you I didn't want a cure?" He sucks in a breath. "What if I told you I wanted to spread it instead?"

"Then I would say well done, Doctor Watson."

It's not Sherlock's voice that answers. They both turn in surprise, eyes drawn up to the figure in the doorway. Mycroft, in full, rich color, smiling like he's won.

 

 

**  
**

"What the hell are you doing here?"

The man ignores him, turning instead to John. "You're looking well, Doctor Watson." He smiles serenely.

"Thank you..." John is looking to Sherlock, gauging for a reaction, and something clicks. "You must be the brother, then."

"Mycroft Holmes. Pleasure. Well, I wish I could say it was a pleasure, but unfortunately my visit -"

"You visiting at all is unfortunate," Sherlock interrupts. At Mycroft's glare, he shakes his head, affecting a sympathetic pout. "Well, what were you expecting, an open invitation? From me?"

"- is one of business," Mycroft finishes, a pointed sniff tacked onto the end.

The malice in Sherlock's voice shifts instantly to curiosity. He pulls himself to his feet and steps closer to his brother. "Yes... what do you mean, 'well done'?"

Mycroft hums, gesturing behind him with his tightly-wrapped umbrella. "Perhaps we should sit down?"

John struggles to stand while his shoulder refuses to help. Neither of them pays him any mind, though - they're locked in some unspoken exchange, minute facial twitches probably all the communication they need. "Don't worry about me," John grumbles as he at last heaves himself up, taking a moment to rest against the countertop. Still no one stirs. "I can make tea?" John finally suggests, just to prove he's still actually there.

"Nope," Sherlock says, and then in a flurry of motion is past Mycroft and perched impatiently in his chair. "Explain," he directs at his brother. Mycroft raises his eyebrows and motions for John to go through before him. He hesitates, but there's nothing the least bit threatening there. At least, nothing yet. He goes to the sofa, leaving the other armchair for Mycroft, which he promptly takes, and then they're staring at each other again.

John nearly rolls his eyes, temper flaring up as the tension thickens into an almost physical force in the room, but before he can say or do anything Sherlock exhales noisily; too long to be a gasp, too revelatory to be a sigh.

"You. This is all you."

John cocks his head. "Sorry?"

Sherlock waves his hand impatiently, and Mycroft interjects. "What he means to say, John, is that I may not have been entirely honest about the circumstances surrounding your injury." Sherlock snorts, and Mycroft throws him a glare before visibly reining himself in. "Would you like to explain, then?"

"I don't have all the facts. Someone has been keeping them from me," he snaps.

Mycroft is unphased. "Very well." He turns back to John. "1998, a small village in rural England. A man reports being able to see in color, colors other than our known variations. Obviously, he's taken as insane, but more cases spring up. Classified government investigation  _Roy G. Biv_  begins, and after more testing it appears a mutation in their DNA allowed for something known as broad-spectrum color vision. The benefits are obvious - new jobs, new art; you can imagine." He sighs, looking more and more uncomfortable as he continues. "But they claimed they needed to do more testing before releasing it to the public."

"So, that's me, then? A guinea pig in your little experiment?" John feels unexpectedly... violated. His hands are shaking in his lap, with anger and an odd sense of disgust, even when he thinks about all the good the color vision has brought him. There's still something so... so fundamentally wrong with being experimented on when he never gave anyone permission, when they could have done anything to him, anything they wanted -

But Mycroft is tilting his head to the side, thinking, and his lips are downturned. "Well, eventually, yes, but not then. You see, the government was somewhat reluctant to release. Eventually I discovered that they were planning on shutting the project down and... exterminating the remnants. Finding a cure became their priority instead, as it tended to spread relatively quickly."

"You'd already seen it," Sherlock guesses, fingers pressed to his chin as his eyes zip over Mycroft's figure. "You would have been killed. They would have killed anyone who -" he stops abruptly, goes a bit paler than usual. He stands and walks to the bookshelf.

A nod. "As such, I and a special initiative decided to take matters into our own hands. Or rather, put them in yours."

Sherlock's got his hands braced down against the shelves and shoulders hunched. John can't see his expression, and he's nowhere near as good as Sherlock at reading people, but there's enough in the harsh line of his back and the strain in his splayed hands to tell that he's not dealing well with the information that he's been tricked. John swallows, and still reeling from his own shock manages to ask, voice low, "And why... why me?"

"Oh, I expect a variety of reasons," Sherlock muses, his own voice snide as it cuts into whatever

Mycroft was going to say. "They would have needed someone just returning to London, with severe enough an injury that antibodies from a blood transfusion of their specially-engineered Sight Infecting sample wouldn't be seen as abnormal, and with enough of a moral principle that he'd arrive at the same conclusion about spreading it, and had enough bravery to go through with it. The last two were a long shot, but as you fit the other categories, John, when your name came up, you probably became something of a perfect candidate."

Sherlock's still got his back to him. It flinches just slightly when John asks quietly, "And you?"

"He could easily monitor my progress, and as a result, yours. He knew I'd at least spread it to Barts, though I'll wager he didn't expect me to be so careful with the sunglasses. I'm spareable in the event it didn't work out, but impulsive enough to have wanted to keep the color for myself."

"And smart enough to evade the rest of the government," Mycroft grants quietly, looking pointedly in his direction. Sherlock's head raises slightly, and John senses that the compliment, strange as it seems, might have been enough to lift his spirits - but when he turns fully, whipping around like a boomerang, it's that old light of deduction in his eyes instead. Almost as good, John reckons, and for the first time in the past ten minutes finds himself relaxing slightly. If Sherlock is back in the game, then all's not over, yet.

"You promised me a week," he says slowly, pacing several slow steps forward, "but you're here barely a few days later." Something dawns in his eyes, bright and sparking against the black of his pupils. "At Barts. The men who attacked us. The government knows about your plan already."

Mycroft's silence is answer enough. John looks from one to the other before rising to his feet. "So what do we do?"

Both of them look at him in surprise. John's eyebrows shoot up at the scrutiny. "I'll assume we're still going through with it. We'd better get a move on if the bloody government is out there searching for us."

Mycroft is looking at him appraisingly, but Sherlock's face has gone unreadable, and stays that way as he says quietly, "Did it occur to you that maybe I don't want to spread it? That maybe I don't care?"

John can hardly believe his ears. He shifts on his feet, blinking, head jutted forward as he works to comprehend it. "Sorry, but weren't you just saying something about being 'impulsive enough to want it'? Weren't you just -"

"Yes, for me," Sherlock snaps. "Why should I care what the people do or don't have? Why do they matter?"

By this point John's taken aback, nearly gaping at Sherlock through a thin haze of anger. "What do they - there are people out there who have no idea what this is, whether -"

"So?"

"Jesus Christ - do you not realize what this means? It could change the entire world." He snorts a laugh, entirely without humor. "I thought you'd be up for it for the sheer idea of overthrowing an entire world order. Seems like your kind of chaos. I thought you'd like the thrill of a world in color, but no, it's just a little experiment for you. Put it back in its box when you're done playing with it, then? Toss it away soon as you've had your fun? God, you're such a child." It sounds nasty to his ears, and he even sees Mycroft flinch at the corner of his vision, but some malicious part of him means it, only provoked by his own exhaustion. The rest of him watches Sherlock's cool regard go absolutely icy and winces at the wreckage all scrawled in the lines of his face.

"Nobody made it my duty to care about all those poor people who will never get to experience a whole new spectrum of color vision, _doctor,_ " Sherlock says, whirling back towards the kitchen and beginning to collect the slides up himself. "I was hired to do a job. More than that, I came to solve a mystery, that's how my mind works and you know it, whether or not my brother lied about it all. That's what matters to me." He punctuates the last word with a vicious rap of his notes and papers on the table, and as he inhales for more of a rant John gets there first.

"Do I matter?"

In the thin line of vision from sofa to kitchen he can see Sherlock, just barely. And shirt askew, forgotten scarf half hanging on his shoulder, red-eyed from the late night and pale as bones, he abruptly looks as if all the life - all the color, even - is draining from him. "You can't."

"But I do." Statement, not question, and he makes it clear. And Sherlock doesn't deny it, looking every bit the child John had just called him but more for the lost way in which his eyes refuse to dip from John's, clinging there stubborn as ever but open and helpless. More vulnerable than he's ever been in the too-short time between this point and their meeting.

"I'm just asking for a new mystery," he says quietly, taking a tentative step forward until Sherlock can meet his gaze over the distance between them. God, they're too tired, the both of them, too young to be doing this. "Solve the color epidemic. Figure out a way to spread it more completely."

"That's not all you're asking."

He should have known better than to think Sherlock wouldn't understand the implications. His breath sighs out of his nose, head dropping forwards as Sherlock begins to step closer, his own head tilted just so. Calculating, precise. A terrible honesty in his gaze.

"You're asking me to betray my nation's confidence. Fine. You're also asking me to leave my city, at least for a time until it all quiets down. A stretch, but I could manage for the right reasons. But what are the reasons? Because, and understand this, John, I'd also be leaving behind my work, everything that makes me function. Do you know how bored I get sometimes? Like the opposite of all that stimulation you mentioned, as if everything is just that one, solid grey. Bleak. Endless. Could you stand me like that? You hardly know, we've really only just met."

He steps again into the living room, just behind Mycroft's chair. "But if despite everything, despite every rational thought to the contrary, I did leave, if I were to uproot everything I am for you, it'd be on some noble quest to restore the world to what you have deemed is its natural order, whether or not we can assume something based on one man's decision. Seems a lot of burden for just two of us to bear. And besides, I don't believe in nobility, John, not for me, so I guess a better question is - do you matter _enough_?"

John is shocked into silence by the end of it, ridiculed and slighted into a corner and crushed under the weight of Sherlock's quiet, simple truths, powerless against the flood of words that issues and overtakes and swallows whole.

"Well," he says at length, and he doesn't look at Sherlock. "That's for you to decide, then, isn't it?" The silence is heady and uncomfortable, and Mycroft, passively silent throughout their argument, finally attempts to restore order, standing up himself.

"Sherlock, John, you must understand -"

And just as he speaks - a crash, smattering of glass on carpet, and Sherlock is lunging and throwing himself and Mycroft to the floor while John flattens behind the coffee table

"What the -" he gasps, all the wind knocked out of him by the impact with the floor. Sherlock, hair dishevelled and looking murderous, rises onto his elbows, slitted eyes fixed on the living room, while Mycroft splutters beneath him. Twisting - and ignoring the reproachful twitch in his shoulder as he does so - he can just see the fluttering curtains where they yawn around the shattered edges of the window. "Someone shooting or throwing?"

Sherlock doesn't answer, instead carefully rolling to the side and sliding out of view from the window as he rises. But when he turns, his mouth firms into a line of grim satisfaction. "Shot." He indicates the hole in the opposite wall of the kitchen, where a bullet has no doubt embedded itself into the plaster.

Mycroft scoots behind the chair, regaining some of his composure with a straightening of his waistcoat. "I have no doubt you'd find it to be from your standard government issue weapon."

Sherlock, ducking carefully from the vantage point of the window, looks up and sneers at Mycroft. "They probably tracked you here, well done."

John's managed to push off to the couch, crawling through the stairwell into the other door of the kitchen and standing, feeling strangely calm despite the fact that there's someone on the street outside with his name on a hit list. Though perhaps... he turns, quizzical expression directed to Sherlock. "Shooting at me, or you, or your brother?"

"Most likely you, you're the liability. Though if they're trying to get to you rather than kill you, it would be me or Mycroft, as we'd get in the way of attempted kidnapping." John thinks privately he sounds far too pleased by the prospect, but refocuses - it's more likely, after all, as he'd said, that it's himself he needs to watch out for. "You okay?" he finds himself saying, despite this.

"Me? Fine." Sherlock's already distracted. "We need to leave."

"Mycroft?" John asks anyway, and Mycroft nods his head wearily, standing up and closing the doors to the kitchen. As the lock clicks, John fixes Sherlock with a curious eye. "Leave? Why?"

Sherlock shoots him a look that could freeze the ice caps twice over. "We're being shot at. The British Government is after you. Either way, Baker Street is no longer safe, not until I find a cure and sort out your mess." The last part is directed as his brother, who is beginning to look impatient.

"Not until you - ?" John manages, still processing that particular piece of information. A small part of him is feeling a bit irrationally despondent by the idea - he'd come to like this place. And after all, he'd sort of agreed to live here. It was, strangely enough, home. The rest of him is watching as Sherlock doesn't dignify him with a response, rather deftly beginning to gather his things from the table, and realizing at last what this means.

"They - the government. You think they won't kill me if you find a cure," he asserts, and watches as Sherlock's face goes strained before it smoothes over just as quickly, like water washing across the surface. It's all the answer he needs. "Oh, Jesus," he breathes, and he suddenly feels a strong surge of remorse as some of his recent words linger in his brain. "Sherlock, I didn't -"

"I can still solve it!" he shouts, rounding on John and sending slides of blood and eyes to scatter over the floor with a wave of his hand. "And I can still save you," he says more softly.

Silence.

He breathes heavily, but abruptly John watches as something seems to unravel in his spine, leaving him weak and slumped. John's hands rise automatically to his arms, mirroring their earlier position, only this time it's Sherlock who now raises his tired eyes up beneath lowered lids; above dark circles. "Hey," he murmurs, for a moment wishing they could both just forget the dangers. For a moment wishing they'd met any other way but in this one. For them, though, he supposes, this was probably always going to be the only way.

"Sherlock, what I said - I'm not a genius." That raises a snarky little eyebrow, at least. "I didn't know what was at stake, and without all the facts I said some things that were a little unfair."

"But true," he interrupts.

"Doesn't mean they were right to say," John replies firmly. "And besides, now you're here, we can change this for them, do a good thing for the world," he says, an infinite gentleness in his tone. "A very good thing."

"If I - if I do it..." Sherlock makes a frustrated noise. "I can't do it for them; don't you see? I don't  _care_  about the world, but I think I would care if you died." He stops, and then says more quietly, like a man in the confessional, "I'm not a good man, John."

John takes a minute for his own response, but it's been there the whole time, obvious almost from the first moment he'd opened his eyes to a curious, lively gaze close and bright against his own. "You're good for me." He lets that sink in for a long, slow moment, eyes not leaving Sherlock's downturned face. "And this isn't over yet. You don't give up that easily. Sherlock, I know that... Mycroft didn't beat you. He had spies and operatives and a whole lot more resources. It wasn't even a real case, not really."

"But if I find a cure, if I can solve that -"

"Sherlock," he chides, still soft. "You can change it. Change the goal. If you make it about spreading it worldwide, that's got to be even bigger, yeah?"

A crooked smile trembles on his lips. "Pitifully easy, actually."

Something in John's chest lurches upwards, a strange fluttering of hope. "So you'll do it?"

Sherlock hesitates.

"Could be dangerous," John murmurs.

Sherlock, after moments of just looking after him, like he's processing something new, finally smirks. "I think I would have enjoyed living with you."

"Maybe one day you can," says John primly, but there's a small grin on his face as well, practically infectious, until the loud clearing of Mycroft's throat reminds them they're not alone.

"So glad to have all that sorted, but can we save the rent talk for later? I would remind you your future home is being surrounded as we speak."

Sherlock glowers, but concedes his point. Then he's straightening, and John sees that old, already familiar light simmering in his eyes, a strong set in the graceful line of his spine, the calculations already whirring about in his brain and visible on his expressive face.

"John. Make sure that laptop is charged. Mycroft - pick up the slides. Can you get us a security detail from your contingent?" At his nod, Sherlock appears satisfied, and turns one more time to John with a grim look resting in the shadows of his face. The rest of him is on fire, remarkable in these moments, the efficiency of his mind something beautiful to behold, and John grins as he goes to do as asked.  _Hell, we're doing this. All or nothing._

 

 

**  
**

A little while later, and Mycroft is ready with Sherlock's laptop, cordoned off safely in the kitchen and biding his time. Their home base, while they stand with beneath the window hatch to the fire escape. John's eyes glimmer palely in the dark. "Ready?"

"Yes."

A breath in the silence, and then Sherlock places his foot in John's cupped hands and legs it up onto the roof, sliding deftly into the space between two chimneys. Below him, yellow light seeps out of the streetlamps and windows, and the buildings are mixes of blues in the darkness, but the sky is already beginning to lighten, the pre-dawn a pale blue itself. Sherlock grimaces. They don't have much time at all. He turns with all the more haste, pulling John up with some effort, though luckily he's strong enough to make it mostly on his own strength. It would come in handy on future cases, he muses,  _army_  doctor and all that.

He stops. No time to think of the future. Not when there's an assassin perched in one of the unassuming houses lining their escape route. He casts his gaze over the street, but at this hour it's mostly deserted, a stray cat slinking along through the shadows and several taxis, even in the middle of the city, the only sign of movement. He indicates the way over the rooftop terraces with a jerk of his head, and then they're off, crouched like extensions of the darkness melting in and out of the early light. He can hear John's easy, unhurried breaths beside him, and the soft pad of their feet picking their way over loose shingles and cracked cement, but it's as if they're alone in the universe, two fugitive souls among the distant hum of a sleeping city.

And it's  _beautiful_ , he realizes as they run. It's not a realization he would usually spend time on, but this time, in this rare moment, it means everything. Because with the day spread out before them, all its golden-blue life and the purpling line of houses snaking away into the distance, and the far-off, hazy glow of the bright silver night-life, and red headlights in the streets and a sliver of orange morning sun as it lances across his now-complete vision, vibrant and right as the earth has never been, and above all the man beside him who is wholly responsible for filling this world with color - because of this, he can see through John's eyes why this is so important. Why this needs to last. Why he must let John go, risk or none at all.

He himself is risking a glance beside him as they slow to a stop, finding themselves on solid ground again at the end of the rows of houses. The secret hatch is just where Sherlock remembers it to be.

"This drain tunnel should take you up to Trafalgar. Wait until it's light enough. They'll have to be able to see the color, for one thing, and I need to enable video uploads on the servers of as many countries as Mycroft and I can manage before your broadcast begins." He pauses, nodding to himself. "And I'll need to call in some favors with the presses first."

"Pretty big favor," John smirks.

The corner of his mouth twitches. "Mmm, journalists are notoriously eager for scoop that sends the world into chaos. Either way, unless you're you with your so-called special blood," John rolls his eyes at the obvious pout in his voice, a prospect he's really quite too put-out by, "it's spread by sight. Unless everyone is going around with their eyes plastered shut, even one person can do a lot of damage. Or good, depending." He's quiet, ruminative, the both of them hesitating over the grate as the sun begins to shake itself up from the night.

"What are you thinking?" John asks, the words hushed but necessary, rushing out like he just can't help himself. Looking at John, he knows that even if this simple, strange, wonderful man could never understand, part of him needs to know. There's this unshakeable certainty that he's meant to be here, at his side, even if it's just to listen.

Looking at John, something mirrors him in his glassy eyes. Something honest and strong, a beautiful truth and a clarity, like the oceans in his eyes are without depth. "By the end this will be unstoppable," Sherlock says, answering him. No need for poetry, not when they have this. "You'll have changed the world, John Watson, for better or worse."

John nods. " _We_  will."

Sherlock's mouth tightens, but his eyes don't stray. "We," he confirms.

 

 

**  
**

When John climbs out of the sewer into a yellow sun, he sees London in full color for the first time.

In the sky, the clouds are cream, golden underbellies offset by a celestial sky blue as they skate around like the hazy figures of boats on the surface of a lake. Beneath them, the high-rises penetrate the vast expanse with their normal charcoal, stainless steel, silver, slate-metal, but at their sides are now buildings of chalky brick red, some with pale, watery yellow siding, some of a pure glass that reflects all the myriad colors of the people and things within its transparent walls.

The people walk streets of cobblestone in patterns of dusted grey and burnt orange and caramel tiles alike. Lampposts are black. Doves are white. But the grass and the trees are speckled in all the variations of green that can be imagined, the solid, gnarled wood of trunks and branches stained brown by weather and erosion. Fire, as he knew now, was all manner of dancing, flickering yellow, darting into orange and bursting into blues and reds as it savaged its fuel.

And when the people - who still see only in black and white, but not for long, not when they meet the watercolored John - turn to look at him in astonishment, their eyes are all manner of blue and green and brown and hazel, rainbows of human emotion that tint them and shade them until it is a vast sea of shifting expression, infinitely deep, impossibly beautiful, all directed at him. A bright splash of colors in the midst of their neutral world.

Some have their phones out already. Good, he supposes. In his arms, the laptop camera blinks, steady as ever, and in a little flat on Baker Street he knows Sherlock waits to send this out to the world. No matter the consequences, he waits for John.

It's a strange sort of comfort, but it buoys him as his arms rise and he smiles into the tiny circle. "Hello, London. Er, hello world, I guess. My name's John, and I'd like to share my story with you." As he talks, he sets off, this strange crowd of people flocking around him, clinging to every word, though they whisper to one another - _look at his eyes. look at his shirt. what_  is  _that?_  - all the while. He spares them a glance every so often, just to make sure people aren't reacting the way people normally do when faced with anything out of the ordinary, but they seem more awed than frightened. Small blessings. He keeps going, circling Trafalgar Square where tourists are likely to be, likely to see and take it home for themselves, spreading it deftly to all the reaches of the world on their boats and planes and cars, speaking into the camera the entire time - his story, what this new color is, anything he can say, anything at all, to reassure and assist in whatever way he can.

He's not stupid, no matter what he might be when compared to someone like Sherlock. He knows that, for a lot of people, this isn't going to go over well. Change almost never does. For some it will terrify, for some he will become the next Typhoid Mary, for some it will be hard to see what was meant to be in the world. They'll demand tests, demand he be locked up, demand all manner of things to keep the world firmly in black and white.

But the world isn't meant to be that way. In this world, there are a trillion variations between the ends of a spectrum that is so much wider than anyone had ever imagined, and he's determined to make sure it stays that way.

"So, um, I guess that's it." He takes a deep breath. In the silence, without his words to stifle it, he can hear sirens in the distance, and there are no doubt far more deadly and silent people coming for him now. Damage control. He looks back at the camera, manages a brave smile. "This is a good thing, I promise. And I know half of you will think I'm mad by the end of this video, but for anyone else who is as amazed as I was to see, see this," he gestures at himself with the unoccupied hand, "then just know that it's been wonderful." He can't stop a little laugh at himself from escaping, but really - he's out in the cool air of a sunny day in London, the world is refracting and reflecting all around him, and he's never seen anything so grand. Whatever happens now, whatever comes next - John has never been certain of much, but he's certain of this. Of his conviction, deep down, rooted firmly to the solid ground, this is right. "I wouldn't give it up for anything. And I -"

"John!"

His head turns at the baritone shout scything through the crowd. Two days, little more maybe, but he'd know that voice anywhere. And it sounds... frightened. It's not even supposed to be here. He can feel where his heart begins to pump more readily against his chest, and he steps forward, uncertain. His face twists in confusion as he searches for him, but now that everyone's in color he's got nothing to go on, even if he's almost ridiculously tall and has that great, flouncy coat of his, and -

A sound he's only heard before in the desert. Something cracks against the back of his skull. He doesn't even have time to gasp, but he recognizes vaguely that other people are screaming for him, so he supposes that's okay. He sways, once, twice, then pitches forward onto the street, asphalt rough against his cheek.

Everything's blurry until he hears that voice again. "Let me  _through!_ " And then there's something warm against his side, something wrapping him up, tugging him closer against it. Oh, someone, then. He tries to focus, but it's really so warm, and getting so dark already. He strains against it - but the color, he needs to see, needs to keep it -

"John. John, please, you have to stay awake." Oh, Sherlock Sherlock's voice, Sherlock's arms around him, and that's definitely his face swimming into focus up above his head as he tries to obey, really tries. But it's hard to keep his eyes open, even harder to keep them trained on the eyes above his own. Ah, those eyes... "Concentrate, John! Someone better be calling an ambulance." That last part's muffled, but he can hear the anger tensing through it. Poor people behind him. Poor him, too, he guesses...

"Shit," he murmurs, trying not to laugh, because if he remembers anything about being shot then it's that there's nothing funny about this, not at all, especially when the back of his head is throbbing and pulsing and the rest of him is going fuzzy. But it's just so... "Couldn't outrun them forever, s'pose" he slurs, "but the timing is crap." The pressure on his arms goes tighter. Sherlock is leaning over him where he's cradled up against his chest, and his eyes are wide and panicked, but John doesn't have any words for him. Who knows how bad it is? And since he's still healing from that last wound, any chance at a good prognosis has just dramatically been cut short. He's still awake, ish. Has to count for something, but again - there's no telling how long that will last, not when it's so warm, sticky warm on the back of his head, and he's fading fast into the comforting arms of that heat.

"Doesn't have to be," Sherlock says, tone clipped. "Don't be stupid and die when we're less than ten minutes from a hospital." It's harsh, but John can feel a thudding against his ear that has nothing to do with his own heartbeat. No, that one is slowing, relaxing...

Sherlock lays a hand against his cheek, directs his eyes up. "John," he says seriously, and that's got to be the millionth time Sherlock has said his name, he knew who he was, Jesus, he's not dead yet, "Keep your eyes on me." Fingers tremble on his skin, and John's eyes flutter, savoring it, but he doesn't allow them to shut. Not yet. He'll try. Ah, dammit. This can't end well, not when that inner voice of his is already so resigned. But two shootings in a matter of weeks? His odds are not looking up.

"I still can't believe you get paid for things like this..." he tries, just to keep himself talking. It seems to calm Sherlock, too, and though he doesn't smile, the wavery line on his forehead stops looking so tense.

"I don't do it for the money."

"It'd be nice, though. Help pay rent."

"It's for fun." He attempts a grin.

"Not the shooting bit." It fails.

"No. Not always." He bites his lip. John can barely make out the line of his teeth where they twist anxiously in his flesh. He thinks privately to himself that it's a shame. "You're going to help me on cases. When this is all over."

It's a nice thought - him and Sherlock, vaulting rooftops, chasing criminals. Rest of their lives. "Yeah."

"Stay _awake_ , John."

"I am, I 'm," he reassures, shifting his hand so one is clasped over Sherlock's grip on his arm. He squeezes, feebly, but it's there.

Sherlock's quiet. Then, "There's so much blood," he murmurs. John doesn't have the energy to lift his head; it's taking all he has as it is to keep his eyes open, but he believes him. Head wounds... bleed a lot, and all. He wants to tell Sherlock that, but it's too many words, his mouth has gone all furry, all he can say...

"...Red?"

Something hot drips onto his face. "Yes."

Sirens. Murmurs. Pool of blood, red blood, the pull of his own darkness, black and inevitable as gravity, even Sherlock's arms not enough to keep him from falling in the end.

All of it fading to grey.

 

 

**  
**

Grey lights. Grey walls. Swimming into focus now are the grey sheets and the grey floors. He closes his eyes again, breathing heavily and disoriented. Why does that feel wrong, why is it -

"Good morning, John. Well, afternoon, I should say," comes a voice from the far end of the room.

His eyes crack open again, and Mycroft tilts his head and smiles tightly. And oh, that's why - his stomach drops. Mycroft's skin has gone white, his crisp suit is grey, his shoes black. Looking around the room, it's the same. The variations are there but no - no color. They failed.

Mycroft obviously senses his struggling, and with a weary exhale he rises from his chair, stepping closer to the foot of the bed. He regards the instruments beeping and humming around him for a moment before returning his gaze to John, and when he does, it betrays nothing. "How much do you remember?" he inquires, shifting his weight and leaning into his umbrella before rocking back again on his heels.

Looking back as best he can, John gets flashes of memory, but the whole story is basically there. "Everything before... no, wait; I was shot," he tries, and then nods, cementing the realization. "I was shot after we tried to spread the new color vision. You can thank your boys for that, then?" he adds, a hard edge creeping into his tone. Mycroft's eyebrows rise fractionally before his whole face smoothes over, and he gives another meaningless smile.

"Yes, the government took care of that. Old officiants; Sherlock's currently following that particular line of inquiry, but you'll have a new order to answer to now."

"Oh, who's that then?"

Mycroft pulls at his tie. "Me."

John's confused, still dazed from pain and the medications for it, but most of his brain is focused on Sherlock now - just Mycroft mentioning his name has John feeling an unexpected tug in his stomach, some mix between not-quite longing and fear. He keeps his voice even as he asks, "So they haven't locked him up for our little... plan?" he decides, delicately, as the alternatives of 'scheme' and 'coup d'etat' are hastily discarded.

A strange, tense silence is his only answer, in which Mycroft continues to survey him without words, without expression. But as he's on the brink of snapping and demanding answers, something seems to be decided, and John ends up feeling like he's passed a test of some sort when Mycroft actually deigns to come around and sit on the edge of his bed, neatly crossing his legs at the ankle, and for the first time throws him a smile that could be considered some form of 'warm.'

"You know, John, the first time we met was like this," he begins conversationally. John isn't sure what to make of it, wary of the shift in character, so he stays quiet, waiting for him to continue. "I didn't know, then, what you two would accomplish together, though I had hoped.

"They haven't 'locked him up,' as you put it," he continues, "because the public won't allow it. Ever since your little video went viral, color has been effectively spreading to all corners of the world. Every country, every city, every household - nearly at least - knows now about the full spectrum of color vision available to us. The formula was a complete success. And the response has been... less negative than we would have predicted. You and Sherlock are something like celebrities. The people's heroes."

"But then why can't I..." his voice trails off. Oh. Oh, God.

When he'd worked in the A&E for his residency, just before being shipped off to the war, he'd seen victims of head wounds unable to see properly, whether they were temporarily blind or had some sort of permanent damage. "The gun shot. It... my color vision?" He's lying in a bed but he feels like he's falling, something plummeting inside him at the thought that though the world might be vibrant and alive around him but he isn't part of it. Not anymore.

Mycroft actually looks sympathetic, something of an apology in his voice as he nods grimly. "I'm afraid the damage disrupted your color receptors. They've no idea if it's permanent, but..." his voice fades into silence, the room suddenly much colder and smaller around them. "You're in color, if it helps at all."

It doesn't, but he nods all the same. It's ironic, or maybe that's misusing the word. Maybe it's just really fucking unfair, after everything. It worked, it worked; he can't actually believe that it worked - just not for him.

"You will eventually be released as normal," Mycroft continues quietly, when the silence has gone on long enough. "Free to live life as you please, Doctor Watson."

John nods, a little dumbly. It seems unreal. He suspects it will for a while yet, but then again, that's probably what everyone in the world is going through as they adjust to an entirely new vision. What's stranger, though, is how he's more concerned with the opposite - how can he go back to normal, after this?

Mycroft is eyeing him shrewdly, and cuts into those thoughts with a clearing of his throat. "I would hope, however, that you take into account what you and my brother have done, together." He hesitates. "He needs you, John."

He laughs away that notion before it can hurt him. "What would he want with me now? My shoulder's still lame, my sight -" His eyes close. Seeing grey is almost worse than seeing nothing at all.

"You know," Mycroft begins after a time, staring down at the tip of his umbrella on the ground. "I worry about my brother. Not because he's incapable, but because he forgets that he is capable himself. Capable of feeding himself, taking care of himself. Capable of caring, and the like." He fixes John with a sharp eye. "I would go so far as to worry about you for the same reason, but not for the same capabilities. In fact, yours match up rather seamlessly. No one else could have done what you have, together. As one. Now... what do you suppose that means?"

It's more soul-searching than he'd be willing to listen to if he weren't on pain killers, but he means every unspoken word when he lifts his eyes to Mycroft and nods, just once.

 

 

**  
**

Sherlock storms back into the building, glowing with the success as he stalks into the center room, eyes on the lookout for his brother. He intends to tell him they've found the government agents responsible for the shooting, and everything can finally, finally be resolved. But it's not Mycroft he finds.

John's smile is brighter than the every star in the sky. "Too busy for a chat about the rent?"

At first he'd been uncomfortable with worrying about someone - the unfamiliar curl of nausea as he sat by his bed, the useless but oddly necessary pacing and fretting in those anxious first hours. Head wounds, even if only grazes, were no small matter. But now when he turns John is there, real and breathing and smiling and alive, and even if he's paler than normal and has gauze strapped around his head and some still wrapped about his shoulder ("Like the fucking Mummy," John will joke later to Sherlock's bemusement, and resulting in his first movie marathon), he is going to be fine. He is going to be fine. He typically loathes repetition, but in this case, it sounds better every time.

He smiles, the grin unstoppable as it overtakes his face. John's own smile widens in response, and Sherlock gives a quiet laugh. Weirdly infectious, this, far more than a bit of color vision. That thought sobers him. John's eyes are as blue as ever, but he knows... "Are you supposed to be out of bed?" The other question, though he doesn't speak it, is present in his gaze.

John shrugs, looking around but not looking like he cares the slightest bit. He's been hospitalized in the closed off government labs where he'd first been on medical leave, and where Sherlock's now been relaying his findings to a team of government scientists. Now he looks around, hardly able to believe how much has changed. Even when it hasn't.

"I'm okay. Really. At first it was... at first, I couldn't reconcile the idea of it," John begins, slowly, staring at where the tunnel vanishes into the dark. "Didn't want to think about it." His gaze falls back to Sherlock, accompanied by a small, soft smile. "But we did a good thing. That's enough."

"They're working on vision more than ever. They might be able to bring it back for you."

But John looks... at peace. "They will, or they won't." His expression changes, shifting into curiosity. "So, you said 'they'... does that mean you're not sticking around for the rest of it?" There's a hesitancy there that's easy enough to read, but it's harder to name the cause. Looking at John, he spies downcast eyes and a stiff spine, and it's almost the textbook picture of apprehension. But surely he doesn't -

"John," he begins, and his voice is oddly earnest, even to his own ears. "The work is what matters to me; keeping myself... stimulated, with problems, puzzles. This isn't a mystery anymore. I've solved it. Now it's just boring."

"But color vision. I'm sure there's more science behind it that needs... discovering."

"Research. Dull. Not my thing."

"But -"

"To whatever you're about to question - who knows? Who cares? But that's what's key - it was you. For some reason you're special. John... you're the mystery now."

John's looking at the floor, but when his face turns up it's trying desperately - and failing - to tamp down around another smirk. "I thought I always was the mystery."

"Different sort."

"Does my kind get boring?"

"Hm," he pretends to consider, but he's come far too close to John for that, his eyes far too crinkly around the edges with mirth at what they've found. "Need more data."

John actually does laugh out loud, relief in the line of his shoulders, and Sherlock can't help but join in. They're quickly cut short by the ringing of Sherlock's mobile somewhere deep in his pockets. After fishing it out, he reads the text.

_Know ur busy w/ all this new color thing. Crazy stuff! But theres another SS w/ note this time. Will u come? - GL_

His eyes flick up to John's questioning ones from the screen. "Remember how you promised to help me on my cases, when all this," he says, indicating the lab space with a flutter of his hand, "was over?"

John tilts his head. "Is this over?"

He spares one last glance at the rooms around them - now full, bustling with people, bursting to the seams with color, though it's the same quiet space as where he first met John, where he first began this case, where the birth of color vision and the extraordinary change that overtook their black and white world began. Paint spilled out of cans to slather the earth in shifting lights. They were out at last. But now what?

Sherlock grins, sharply, showing too much teeth and feeling positively radiant, as the quiver of excitement, of the chase, begins to take root. "It is."

But as John falls into step at his side, slotting easily into place, he knows something even greater is just beginning.

 

 

**  
**

Sometimes, John sees flashes. The first time he shoots a man for Sherlock, the gunshot is yellow and bright. He'll sometimes catch Sherlock's gaze and see it slipping like a trout in a stream through his changeable eyes. A splash of Mrs. Hudson's purple dress, a blue autumn sky. Their first kiss and he's got his eyes wide open and sees no colors at all, but it's beautiful all the same. Win some, lose some, he guesses.

In his dreams, they're still there, little blooms of color like that first night. Once he has the same dream, only this time as he takes Sherlock's hand the world refracts like a kaleidoscope, beautiful, and when he wakes the memory is still imprinted on the backs of his eyelids.

That time, though, it doesn't matter, to slip back into sleep and lose it again. Sherlock's curled against him, breath warming the nape of his neck, sleep-heavy arms pressing him back into his chest. It's all morning-soft and quiet on the London streets as the sun laps just at their edges. And even if, for John, it's all gone grey, he reckons Sherlock manages to fill his world with color anyway.

Dawn breaks. The red sun spills in from the window and floods the room with light. They sleep on.

**Author's Note:**

> Sources, because I like doing my research:
> 
> [here](http://faculty.stcc.edu/AandP/AP/AP2pages/Units14to17/unit15/retina.htm) and [here](http://webvision.med.utah.edu/book/part-ii-anatomy-and-physiology-of-the-retina/photoreceptors).
> 
> Thanks for reading! If you're feeling particularly kind, maybe wish me luck on the contest? ;)
> 
> 101312 - Dzenka pointed out some issues with my use of a shell casing where one couldn't possibly exist, so that's been fixed. Thanks, love! Also, my infinitely stupid jugular vs. carotid error has been amended as well.

**Works inspired by this one:**

  * [Cover for The Grey Matter by anchors](https://archiveofourown.org/works/5223620) by [gurkenpflaster](https://archiveofourown.org/users/gurkenpflaster/pseuds/gurkenpflaster)




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